In AgCl1-xBrx electron-hole recombination occurs preferentially at bromine sites. For small x this recombination gives rise to formation of an exciton which may be described as (AgCl5Br)5-. The lowest triplet state of the exciton decays radiatively to the ground state with emission within a band at 2.47 eV and the structure of the exciton may be investigated by ODMR techniques using this emission. The present investigation shows the existence of dynamical effects arising from Jahn-Teller coupling in the emitting triplet state, and that these effects change as x changes from 0.001 to 0.02, owing to increasing lattice strain. The Jahn-Taller model has made possible the identification of lines in the ODMR spectrum previously unassigned and accounts for zero-field ODMR measurements reported by A. Marchetti and D.S. Tinti (1981).